The invention relates to brake drives (reverse brakes) which can be employed in many engineering sectors, for example as adjusting and fixing devices in machines, medical instruments and equipment, sports and household devices, control mechanisms, for chairs and other items of furniture, in vehicles, aeroplanes, car seats etc. These brake drives can be actuated by both a hand wheel 6 and by a control lever (6a in FIG. 5) or by electrical, pneumatic, hydraulic or any other switching or control elements which are not shown.
The object of the invention is to create brake drives which can be designed in a simple and cost-effective manner owing to their construction and optimal brake pressure distribution, and can also be designed in plastics material, zinc injection moulding or aluminium injection moulding, i.e. from less rigid material (parts 1 to 6a) and can be adjusted and fixed by both a hand wheel (6) and by a control lever (6a in FIG. 5) or by electric, pneumatic, hydraulic, magnetic or any other switching or control elements (not shown) from the primary or drive side xe2x80x9cby entraining the drive side, for example shaft 3xe2x80x9d in both directions, in other words against a blocking or braking force, with the smallest amount of slippage between primary rotational movement (adjustment or actuation) and secondary reverse locking or movement, for example at a drive or driven shaft 3. A forward or reverse movement, each rotational movement of the drive and driven shafts can be severely braked or completely blocked and released again as quickly as desired and at any time depending on the design and adjustment. The disadvantages or weaknesses of brake drives and overrunning-type brakes according to the current state of the art are avoided by the subject of the invention.
Up until now, brake drives had inter alia multi-threaded cylindrical helical springs as braking element, which springs gradually expand along a stationary drum cylinder from one spring winding to the next owing to circular pressure (for example anticlockwise) on one of the two spring ends in a stationary drum cylinder until all windings are gradually jammed against the stationary drum and block further rotation in the same direction. Owing to a circular tensile force at the other end of the same brake spring (understandably only with slippage with respect to the preceding circular force of pressure at the other spring end), the individual spring windings can gradually be spooled onto a smaller cylindrical external diameter of the spring and jamming or blocking against rotation of the spring and therefore of a potential drive shaft are gradually cancelled only with an undesirable slippage path.
This dead rotational slippage between releasing, rotating and blocking in previous reverse brakes constitutes a big disadvantage compared with the present xe2x80x9cBrake drivexe2x80x9d invention.
A further disadvantage of these multiple springs is that only a very thin, circular, external line of the individual helical spring windings, in other words a very small face, is supported on the housing inner cylinder, as a result of which, a high rigidity material such as steel or the like must be used as a spring and also for the brake drum (as a large specific force has to be exerted by the mini-friction face of the spring onto the cylindrical friction face).
A further significant disadvantage is that xe2x80x9ca large amountxe2x80x9d of unused space and unused cylindrical friction face of the housing, in other words unused brake drum face between the thin actual spring friction faces, is wasted between the very thin, helical friction faces of each individual helical spring winding supported tangentially on the brake cylinder.
The hitherto conventional overrunning roller-type or overrunning ball-type brakes require a similar waste of space and unnecessarily require an extremely high level of material rigidity (and are therefore generally made of steel and with expensive, and the highest levels of precision), which brake types all operate only with point application in terms of material even when the largest braking or blocking force is desired.
Shoe brakes have the disadvantage inter alia that their cylindrical friction faces are constantly rigid in diameter and in the curvature with the housing internal cylinder curvature do not achieve a really saturated specific force of pressure applied uniformly to the entire brake periphery or cannot guarantee this over a prolonged period of time. For this reason, nearly all shoe brakes must comprise an additional compressible material (the brake linings) between the shoe brake face and the drum inner cylinder brake face which also has to be replaced with prolonged use.
Advantageous embodiments of the present xe2x80x9cBrake drivexe2x80x9d invention are provided in the patent claims and sub-claims and the drawings and, in brief, provide the following advantages:
1. Both xe2x80x9cactivexe2x80x9d brake cylinder faces 5 are many times larger because they rest on one another xe2x80x9cwith their entire facesxe2x80x9d without unused intermediate spaces and therefore can be used 100%.
2. As a result, the specific surface pressure (per mm2) is so small that even plastics material, aluminium, zinc or other injection moulded materials or less rigid materials and more favourable production methods can be used for the active elements.
3. The expanding ring 2 has no no-load operation (slippage) between blocking and releasing because (like a helical spring) it does not have to wind or unwind over a plurality of spring windings when it receives a circular push at a brake cylinder end of the expanding ring to radially enlarge the diameter or the brake force and inversely, receives circular tensile force at the other pitch circle end of the brake cylinder once to reduce the expanding ring diameter and therefore to lift the brake in order to be able to adjust the brake drive.
4. The entire one-piece expanding ring (see FIG. 1) can also be designed as a double ring as in FIG. 3 and with and without additional expansion springs (9, 9xe2x80x2, 9xe2x80x3, see FIG. 2) and can also be of multi-layered laminated design and despite this retains all the advantages of the new brake drive.
5. The expanding ring 2 which, with its larger external cylinder diameter, was squeezed upon installation into the smaller internal cylinder of the brake drum 1, has (in contrast to rigid shoe brakes) the active snap force (expansion force) at all points of its friction cylinder periphery, in addition to the normal application force, to convert itself from a smaller radius into a larger radius by means of its inherent tendency and its stored force.
Owing to the previously mentioned advantages alone, the brake drives according to the present invention rarely have any undesired slippage between control and blocking or braking any more, and this is in both primary and secondary terms, in other words at the input and at the output side.
6. Further advantages are given by an additional increase in the brake force of the brake drive inter alia by, for example:
a) keyway-shaped inner and outer faces between expanding ring and housing (transverse to the cylinder face, see FIG. 4 on the brake faces 5) as a result of which an additional snap and braking effect or blockage is produced by the tapered rings in the opposing keyways at the entire periphery, as is the case with a V-belt.
b) Owing to symmetrical or asymmetrical micro or normal waviness of one or both friction faces, in longitudinal direction or direction of rotation of the circular brake faces (see FIG. 3, circular pictures a and b), a complete standstill against a rotation is achieved between drum 1 and expanding ring 2 with the slightest expansion, and running is again achieved with slight compression of the expanding ring.
c) Owing to such a symmetrical or asymmetrical micro- or macro-waviness of one or both friction surfaces, or micro- or macro-waviness extending in another way, an ideal state can be achieved for many purposes, for example, in such a way that the brake drive itself (in other words, without but also with xe2x80x9ccounter-torquexe2x80x9d) has a larger braking moment, for example in the anticlockwise direction (or clockwise direction) than in the other direction of rotation. As a result, the torque for lifting a crane load, for example, can be designed so as to be smaller than that for rewinding the cable pull or other drive. The reverse movement is actually more sluggish than the lifting or tensioning process of, for example, a cable pull or other drive. This can also be achieved, for example, by an asymmetric sine curve or the like which is gentler in direction of rotation, in other words flatter, and is steeper in the reverse direction and therefore has more braking power.
d) When the direction of rotation in which the brake drive should brake or block is known, a starting aid can be provided at that end of the expanding ring friction face which is remote from the pressure point of the driving journal 4 on the circular end face of the ring 2 and which is not pushed by the part 4 itself, for the start of braking after a lifting process, in other words a braking aid for the transition from the lifted expanding ring position to the expanded, braked or blocked position (similar to a trimmer in ships, aeroplanes, etc.), by start braking aids (see FIG. 3, parts 12 and 12a).
xe2x80x83The parts 12 are ribs which project slightly beyond the brake cylinder of the expanding ring 2 which, after lifting in the event of a further braking or blocking wish, start to brake as first parts of the expanding ring 2 owing to their early contacting of the brake drum inner cylinder 5 (and also owing to their additional tilting). As a result, the remaining arc of the circle and brake face are brought more quickly and violently into close contact and the entire ring is expanded or blocked as in a chain reaction.
xe2x80x83The start braking aids 12a operate in a similar manner. They comprise one or more additionally inserted or vulcanised-on, glued, dipped coatings with materials which project slightly and have a higher coefficient of friction.
7. An expansion element (see FIG. 6b) which has been produced from slightly resilient material and has also been squeezed, with excessive diameter into the brake drum 1 and can only receive counter-torques in xe2x80x9conexe2x80x9d direction of rotation, can be rotated in both directions by a pivoted lever 6a (in other words, also against the block) when owing to actuation of the lever or a pulled-on hand wheel etc., a shrink ring 13 can be reduced in diameter until the resilient expansion element 2b with its segment indentations 14 is reduced in diameter by the shrink ring 13, which is cast or located in a groove, until it is loosened or lifted such that the pivoted lever 6a together with the expansion element 2b can rotate in the stationary brake drum 1 which in turn then drives the driven shaft 3.
8. To increase the expansion force of the expanding rings 2, expansion force intensifiers can be used (parts 10 in FIGS. 5, 5a and 5b) which intensify the braking or blocking force of the expanding ring owing to the counter-torque of the driven shaft 3. Owing to, for example, contracting elements, such as the two contracting journals 6xe2x80x2 and 6xe2x80x3, which, for example, are securely connected to a contracting pivoted lever 6a or are integral therewith, both the expanding ring 2 and the expansion force intensification lever 10 or expansion force intensification eccentric 10xe2x80x2 and the shaft 3 can be reversed, a contracting clearance 11 (play between brake internal and external cylinder) can be created and the rotational position of the shaft 3 can also be adjusted and fixed again in both directions of rotation by means of its driving journals 4 with the same pivoted lever 6a or instead of that, a pulled-on pivoted hand wheel (with the same contracting journals 6xe2x80x2 and 6xe2x80x3).
9. The secondary reverse torque presses in a circular manner exclusively on the inner end face of the expanding ring 2 via the shaft 3 and its driving journals 4 in such a way that it can only exert a torque on the expanding ring on the end face of the expanding ring ends in a radially-pushing manner. Owing to the actuating element or elements, this power arm lever can be used to adjust a brake drive and to restrain a circular force, in other words for braking or blocking a torque or rotating a shaft.
The brake drive is installed as an embodiment in FIG. 1 to FIG. 4 in the free interior of a conventionally hollow hand wheel (part 6) which can also be mounted, for example, for actuating or adjusting a car or office seat or any machine or any device, or with which a torque force automatically braked or blocked against reverse movement or rewinding is to be controlled.
Such a hand wheel (part 6) or such an adjusting lever (part 6a in FIG. 5) or even just the brake drive alone (with or without other actuation elements) can be adjusted in both directions of rotation with driving of the shaft (part 3) without additional lifting of a brake or overrunning or other type of brake or blocking device. When the hand wheel or the lever or actuating element for the brake drive is released, the brake drive brakes or blocks automatically, in other words (depending on the adjustment and/or design, pre-tensioning, material use etc.) the brake drive cannot reverse the adjusted rotational movement in a secondary retroactive manner or can only do this in a severely braked fashion, from the driven shaft 3, after an adjusting force has been released after a primary adjustment (by the hand wheel, the lever etc.).
The brake drive can, however, also be located inside any design at any point of a drive shaft or driven shaft (supported against external torque by the environment or a cable pull, a spoke or other anchorage) in such a way that the primary adjusting rotary force acts (primarily, in other words in an adjusting fashion), for example, by means of a second hollow shaft (not shown) (pulled over a projection of the first shaft 3) acting on the same axis or an adjusting shaft extending in an articulated manner at an angle to the main axis, but equally for example, by means of a cable reel and Bowden wires, toothed wheel or other drive mechanisms inside a device, equipment, furniture, vehicle etc., wherein the driving or driven outgoing shaft 3 can be adjusted with the primary adjustment. Inversely, in other words secondarily, this shaft 3 cannot, however, (or, depending on adjustment, with greater or less ease) rotate this brake drive.